had a look at the V8 lexus SC400's (i.e soarer) which have the 10" powered sub in the rear parcel shelf and was wondering how you would make the boot into an effective sub box.... so i went to jaycar and got a vemon 10" sub and when to work..... found there was all ready a cap'd off cutout in the rear shelf but was a little to small for the venom, assuming they use a 10" papercone style woofer as a sub in the V8's????.......
made a base for the sub and sikaflex'd it down and foam-a-filled the rest of the parcel shelf......
that is about the extent of what ive done and well would like some input into how i can use this to make a decent sub box?????

you could use a sub that suits IB and seal off the boot from cabin, or build a box under the parcel sheft for it.

box under shelf would be my go I've seen it done and quite affective

The standard sub is paper cone and verry cheap and nasty, also it is Infinate Baffle (free air) sub meaning it doesnt need an enclosure, just a baffle plate separating the front from the back. the venom sub you have requires a enclosure or box to peform at its optimal. so yeah i agree with tom and build a box under the parcel shelf.

i really wish it was that simple atm the is about (maximum) 4mm between my fuel tank and the magnet on the sub :/
ill post some pics to make it easier to explain

Yeah i know i saw it on the cruise when you opened the boot. You dont have room to build a box under there, i think your only chace of getting decent bass is to build a box in your boot and put mesh over the hole in the parcel shelf to let the bass through into the cabin. probably not what you want to hear but i think its the only way.